Supports for securing the head of a patient for surgical or radiological procedures are known in the art. The supports are typically adjustable so the head of the patient may be secured in different positions for different radiological views or to facilitate access to a patient's head during a surgical procedure. Such head supports typically include a support beam adapted to be mounted outward from one end of a patient support table, a head clamp, and one or more intervening adjusting members for adjusting the height and orientation of the head clamp with respect to the table. Such head supports are disclosed in U.S. Pat. Nos. 4,545,572 and 4,169,478 which are assigned to the assignee of the present application and commercialized by Ohio Medical Instrument Company, Inc. as the Mayfield.TM. Headrest.
The components of such head supports have usually been fabricated from stainless steel or other metals. One problem with head supports comprised of metal components is that the metal is radiopaque to x-rays which produces "artifacts" in the x-rays taken when the headrest is interposed between the x-ray source and the x-ray film. These artifacts are created by the metal head support components blocking the path of the x-rays as they travel from the source to the film. The areas of the x-ray film that remain unexposed because the x-rays are blocked by the head support appear as artifacts in the developed x-ray picture. These artifacts diminish the usefulness of the developed x-ray picture because they obscure the image of a portion of the head that normally would be viewable, absent the obscuring head support component.
The use of radiolucent materials which permit x-rays to pass through them have been used in known head supports to reduce artifacts. While the x-ray pictures produced by using these head supports have fewer artifacts, they present other problems to the radiologist. Specifically, most known head supports are mounted to one end of the patient support table at or near the center of the table's width with mounting rails. The mounting rails are made from radiopaque materials because the radiolucent materials are not sufficiently strong enough to rigidly hold the head support. While the radiolucent material of the head support components permits most of the x-rays to pass through, the mounting rails do block part of the x-rays which results in a smaller artifact but one which can obscure finer details in a developed x-ray picture. What is needed is a way of reducing the number of headrest components that are interposed between the x-ray source and the x-ray film.
Another problem with previously radiolucent head supports is the difficulty of mating an adjustable head support made from a radiolucent material to another component made of radiolucent material so the two components do not slip relative to one another under the pressure exerted by the patient's head. Slippage occurs because the surfaces of the radiolucent material have lower coefficients of friction than those of the metal surfaces in previously known head supports. While circumferential collars and grooved surfaces have been previously used, they require machining and the incorporation of tightening devices such as threaded bolts and apertures. What is needed is a simple way to maintain a mating relationship between head support components made from radiolucent materials.